02 sensors

Jonathan R. Lusky lusky at knuth.mtsu.edu
Thu Jul 20 04:25:31 GMT 1995


Michael Kent writes:
> 
> Yesterday I had a chat with a tuner in the LA area who said he had done 
> some back to back tests of a Bosch sensored Haltech A/F meter and a 
> Horiba. He found that the Bosch 3 wire sensor worked ok on the lean side 
> of stoch as long as the EGT stayed constant. If there was any kind of 
> change in EGT the indicated A/F would change on the Haltech but not the 
> Horiba. The DFI injection system was programed to keep a constant 12:1  
> over the test window.
 
That was my experience too...  I was also using a 3-wire Bosch and
Horiba MEXA101L on the same vehicles.  I could trust the Bosch HEGO
pretty well between .95L to 1.05L or so.  Outside of that range it
was pretty useless.  On my CNG vehicle it was also fairly consistant (altho
very nonlinear) on the leaner side even outside that range.  On my M85
vehicle, I could create conditions where 600mV on the HEGO at one load
(and EGT) was actually significantly richer than 800mV at a different
load (and EGT).

> I would like to know what others have found out about the accuracy of 
> these inexpensive A/F meter set-ups. 

Those inexpense meter setups are just a $35 generic HEGO and a cute
bargraph voltmeter.  None of them work worth a flip if you need
accuracy away from stoich.

> The idea of getting a multi thousand 
> dollar Horiba is *way* out of the question for a mortal like me. If the 
> cheap meters aren't accurate why use poor information?

You can always do it the old fashioned ways...  timeslips, reading
plugs, and/or checking EGT's.  The HEGO still works great for idle
and low-load tuning, however.

-- 
Jonathan R. Lusky                        lusky at knuth.mtsu.edu
http://www.edge.net/~lusky/                 (615) 726-8700
-------------------------------------   ------------------------------
68 Camaro Convertible - 350 / TH350  \_/ 80 Toyota Celica - 20R / 5spd



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